Ball grinding and lapping machine



May 19, 964 R. M. CHAPMAN 3,133,383

BALL. GRINDING AND LAPPING MACHINE Filed June 12, 1961 3 Sheets-Sheet 1 FIG I INVENTOR. RICHARD M. CHAPMAN ATTORNEY y 1964 R. M. CHAPMAN 3,133,383

BALL. GRINDING AND LAPPING MACHINE Filed June 12, 1961 s Sheets-Sheet 2 52 E I w 54 mug-m INVENTOR.

RICHARD M. (JHAFMAN ATTORNEY May 19, 1954 R. M. CHAPMAN BALL GRINDING AND LAPPING MACHINE 3 Sheets-Sheet Filed June 12, 1961 INVENTOR. RICHARD M. CHAPMAN ATTORNEY United States Patent 3,133,383 BALL GRINDING AND LAPPING MACHINE Richard M. Chapman, Arcadia, Califi, assignor to North American Aviation, Inc. Filed June 12, 1961, Ser. No. 116,331 8 Claims. (Cl. 51-117) This invention pertains to a means for precisely grinding, lapping, and smoothing the surface of a spherical or truncated spherical ball. More particularly, the device of this invention is adapted to grind and lap the surface of a metallic ball to make it precisely round and smooth.

In modern instrument manufacturing it is frequently necessary to grind and polish spherical surfaces to a high degree of circularity and smoothness. For example, certain gyroscopes have their rotors spun upon air bearings whose surfaces must be precisely spherical to allow slight precession of the rotor. Usually the spherical rotor surface is a truncated spherical surface.

The surface may in small quantities, be ground, lapped, and polished by hand.

It has been necessary to manufacture spherical and truncated spherical sunrfaces in quantity lots. Prior known machines could not grind and lap the spherical surface of the required balls with suflicient rouudness and smoothness.

The machine of this invention is adapted speedily and accurately to grind, lap, and polish the spherical portions of the surface of a ball.

It is therefore, an object of this invention to grind, lap, or polish the surface of a spherical member.

It is a more particular object of this invention to grind, lap, or polish the surface of a spherical ball.

It is also a more particular object of this invention to grind, lap, or polish the surface of a truncated spherical ball.

More particularly, it is the object of this invention to perform the above named objects with extreme accuracy of roundness and smoothness of the spherical member.

It is likewise a particular object of this invention simultaneously to rotate and lap, grind, or polish a spherically shaped surface on zonal surfaces of the sphere with an oscillating random grinding motion.

Other objects will become apparent from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is an isometric view of a typical embodiment of this invention;

FIG. 2 is a plan view, partially in schematic, of the device of FIG. 1;

FIG. 3 is a view, partially in section, of a typical means for rotating the grinding cups used in this invention;

FIG. 4 is a view, partially in section, of a typical oscillating grinding cup used in this invention;

FIG. 5 is a view, partially in section, taken at 5-5 in FIGURE 4; and

FIG. 6 is a profile View of the oscillating member of FIG. 4 shown in its retracted position.

Referring to the figures, a spherical or truncated spherical ball 10 is contacted by three cup members 12, 14, and 16. Each of cup members 12, 14, and 16 contact ball 10 on a circular surface, i.e., a line or zonal surface contact, one of which is shown at 18 in FIG. 2. A grinding or lapping compound (not shown) is applied to ball 10 to cause the internal surfaces of cups 12, 14, and 16 to 3,133,383 Patented May 19, 1964 grind or lap ball 10 in the zonal region of contact. Cups 14 and 16 rotate in a direction to reinforce each other in the torque they apply to ball 10. Grinding cup 12 rotatably oscillates about the polar axis of its zonal contact region (preferably through 360 degrees) to cause various portions of ball 10 randomly to contact the grinding surfaces of cups 12, 14, and 16.

Cups 14 and 16 are driven by motors 20 and 22 through belt drives 24 and 26 and through bearings 28 and 30. It is to be stressed that cups 14 and 16 may conveniently be driven by a single prime mover. In FIG. 3, belt 24 drives spindle 42 in universally mounted bearing 28. To maintain tension in belt 24 and to prevent belt 24 from moving bearing 28, motor 20 is mounted upon a frame 49 which is pinned for rotation at 51. A strut 47 between bearing 28 and frame 49 force-balances the tension of belt 24 to remove torque from the outer structure of bearing 28.

The oscillation of cup 12 about the polar axis of its zonal contact area is caused by motor 32 which drives the bell-crank mechanism 34 to cause shaft 36 to oscillate through a complete turn about its axis of rotation. Shaft 36, through belt 38, drives spindle 40 and grinding cup 12.

In the preferred embodiment of this invention three cups, substantially in the same plane are symmetrically disposed degrees apart) about ball 10. Although three grinding cups 12, 14, and 16 are sufiicient to achieve the desired results, it is apparent that additional cups can be utilized.

Each spindle 40, 42, and 44 is connected rotatably to drive spindles 12, 14, and 16, respectively in rotation about the polar axes of the zonal surfaces of contact betwen the grinding cups and ball 10.

Spindles 42 and 44 are universally mounted to allow grinding cups 14 and 16 to seek their own angular positions upon the surface of ball 10. In the embodiment of FIG. 1 spindles 42 and 44 are mounted in journal bearings 28 and 30 for complete rotation about the polar axes of the zonal grinding surfaces of cups 14 and 16. The remaining two degrees of freedom are about the axes of shafts 64 and 66 and the axes of trunnions 48 and 50. It is to be emphasized that other types of universal mountings may be employed. For example (in an embodiment not shown) spindles 42 and 44 could be spline-driven and universally mounted upon a ball type thrust bearing.

A parallel linkage 52 is adapted to retract grinding cup 12 from ball 10 to allow ball 10 to be removed. Parallel linkage 52 also is adapted to apply force to ball 10 to cause ball 10 to engage the zonal grinding surfaces of cups 12, 14, and 16. Parallel linkage 52 is shown in FIG. 1 with the grinding cup 12 engaging ball 10 and in FIG. 6 with grinding cup 12 retracted from ball 10. In FIG. 1 the weight of linkage 52 biases grinding cup 12 into engagement with ball 10. Additional weights 54 optionally may be utilized to increase the force between grinding cup 12 and ball 10. A locking member 5 6 conveniently may be used to lock grinding cup 12 into its retracted position against the torque applied by weight 54.

In 'FIG. 1, the device of this invention is shown sitting on a table 60' with an oil sump 62 immediately below ball 10 to catch drippings therefrom. Spindles 42 and 44 are shown universally mounted upon shafts 64- and' 66 and swivel bearings 48 and 50.

In FIG. 4, bellcrank mechanism 34 is driven through a pulley arrangement 72 by motor 32. The structure of the bellcrank mechanism may be better understood by referring to FIG. 5.

In FIG. 5, motor 32, through pulley 72, drives the shaft 74 of bellcr-ank 76. Bellcrank 76 drives rackgear 78 which engages gear 77 on the shaft 80. Rackgear 78 rides upon rollers 79 and 81. Shaft 80 drives belt 38 which, in turn, drives spindle 40 and grinding cup 12.

It is to be understood that grinding cup 12 may have axial force applied to it and it may be retracted parallel to the polar axis of the zonal grinding surface by mechanisms other than the parallel linkage mechanism 52.

The parallel linkage mechanism 52 may be examined more closely by referring to FIGS. 4 and 6. In FIG. 4, latch 56 is disengaged which causes weight 54 and the unbalanced structure of the cantilevered weight support 82 to apply an unbalanced torque to lever 84 about pivot 86. Lever 84 is connected to journal bearing 88 at pin 90. Bearing 88 supports spindle 40 to cause force applied by pin 90 to be directly axially along spindle 4t) and to grinding cup 12 along the polar axis of the zonal contact region thereof.

In FIG. 6, weights 54 and the unbalanced portion 82 or parallel linkage 52 are forced upward which forces, through pin 91, bearing 88 to be retracted from ball 10. The retraction of bearing 88 also retracts grinding cup 12.

In operation, grinding cup 12 is retracted into the position shown in FIG. 6. A ball or truncated ball to be ground is inserted into the zonal cups 14 and 16. Latch 56 is then disengaged to allow the weight 54 and the unbalanced portion 82 of linkage 52 to force grinding cup 12 into engagement with ball 10. Power is then applied to motors 22, and 32. It is to be understood that one motor could be utilized, together with appropriate linkages, to drive spindles '42 and 44 and bellcrank mechanism 34. Abrasive compound (not shown) is then applied to ball 10. The drippings are caught in sump 62. The rotation of grinding cups '14 and 16 about polar axes of their zonal contacting grinding surfaces in the direction shown by arrows 90 and 92 causes the torque transmitted to ball 10 to move ball 10 in the direction shown by arrow 94. That is to say, the directions of arrows 90 and 92 are such that the torques applied by cups 14 and 16 reinforce to rotatably drive ball 10 in the direction shown by :arrow 94. The operation of hellcrank mechanism 34 causes cup 12 rotatably to oscillate, preferably 360 degrees, about the polar axis of its zonal grinding surfaces, as shown by arrow 96. Because of the variable friction between the grinding cups and ball 10, ball 10 is caused to move randomly relative to the grinding cups which causes ball 10 to be uniformly rounded and smoothed.

When the grinding of ball 10 is completed, latch 56 is moved into the position shown in FIG. 6, which retracts grinding cup 12 from ball 10 and allows ball 10 to be released.

Thus, the device of this invention is a grinding machine which is particularly adapted precisely to grind and lap spherical balls to create a ball of precise curvature and smoothness.

Although the device of this invention has been described particularly above it is to be understood that the invention is not to be limited by the above description but only in accordance with the spirit and scope of the appended claims.

I claim:

1. Means for grinding a spherical surface comprising: at least three grinding cup members each shaped to have substantially the same curvature and positioned to engage a spherical surface in a plurality of zonal regions; mechanical means for rotatably oscillating at least one said cup member about a polar axis of its said zonal region, mechanical means for rotating the remaining said cup members; and mechanical force means connected to one of :said cup members for urging said one of said cup members against said spherical surface and urging said spherical surface against the other of said cup members.

2. Means for grinding a spherical surface comprising: first, second, and third grinding cup members each shaped to have substantially the same curvature and positioned to engage a spherical surface in a first, second, and third zonal region; mechanical means for automatically rotatably oscillating at least one said cup member about a polar axis of its said zonal region, mechanical means for automatically rotating the remaining two cup members in directions to cause random grinding of said spherical surface, and means for mechanically applying an axial force to at least one of said cup members.

3. Means for grinding a spherical surface comprising: first, second, and third grinding cups each shaped to have substantially the same curvature and positioned to engage and support a spherical object in a first, second, and third zonal region; mechanical means for rotating two of said cups about the polar axes of their respective zonal grinding regions, means for supporting said two of said cups for universal freedom of rotation, and mechanical means for rotatably oscillating said remaining cup that is not rotated, about the polar axis of its zonal grinding region.

4. Means for grinding a spherical surface comprising: first, second, and third grinding cups each shaped to have substantially the same curvature and positioned to engage and support a spherical object in first, second, and third zonal regions; mechanical means for rotating said first and second cups about the polar axes of their respective zonal regions in directions to reinforce each other in the torque transmitted from said cups to said object; means for supporting said first and second cups with universal freedom of rotation; and mechanical means for rotatably oscillating said third cup about its polar axis.

5. Means for grinding a spherical surface comprising: first, second, and third grinding cups each shaped to have substantially the same curvature and positioned to engage and support a spherical object in first, second, and third zonal regions, the polar axes of said regions being substantially coplanar; mechanical means for rotating said first and second cups about the polar axes of their respective zonal regions, in directions to reinforce each other in the torque transmitted from said cups to said object; and mechanical means for rotatably oscillating said third cup about its said polar axis.

6. Means for grinding a spherical surface comprising: first, second, and third grinding cups each shaped to have substantially the same curvature and positioned to engage and support a spherical object in first, second, and third zonal regions, the polar axes of said zonal regions being substantially coplanar and displaced substantially apart; means for rotating said first and second cups, about the polar axes of their respective zonal regions, in directions to reinforce each other in the torque transmitted from said cups to said object; means for rotatably oscillating said third cup about its polar axis; two of said cups eing pivoted for universal freedom of rotation, and said third cup being pivoted for freedom of rotation about an axis substantially perpendicular to the plane of said polar axes and adapted to translate along its said polar axis.

7. A device as recited in claim 6 and further comprising means for applying a force to said translatable cup, controllably to urge said translatable cup towards said object to force said object into engagement with said cups.

8. Means for grinding a spherical surface comprising: first, second, and third grinding cups, each shaped to have substantially the same curvature and positioned to engage and support a spherical object in first, second, and third zonal regions, the polar axes of said regions being substantially coplanar and circumferentially displaced about said objects in a substantially symmetrical pattern; means for rotating said first and second cups, about the polar axes of their respective zonal regions, in directions to reinforce each other in the rotation torque transmitted from said cups to said object; means, including a bell-crank mechanism, for rotatably oscillating said third cup about its References Cited in the file of this patent UNITED STATES PATENTS polar axis; said first and second cups being adapted to 1,042,794 Irwin 1912 pivot for freedom of rotation about parallel axes perpen- 5 2787093 sundbefg 1957 dicular to the plane of said polar axes; said third cup 35024578 Mushkm 1962 being adapted to translate along its polar axis; and force means, connected to said third cup to apply a force to OTHER REFERENCES said third cup along its polar axis to urge said third cup Making Crystal Spheres from Review of Scientific into engagement with said objects and fonce said object 10 Instruments, vol. 25, 1954, page 401. Copies in Scieninto engagement with said first and second cups. tific Library and Div. 58 (51-289). 

1. MEANS FOR GRINDING A SPHERICAL SURFACE COMPRISING: AT LEAST THREE GRINDING CUP MEMBERS EACH SHAPED TO HAVE SUBSTANTIALLY THE SAME CURVATURE AND POSITIONED TO ENGAGE A SPHERICAL SURFACE IN A PLURALITY OF ZONAL REGIONS; MECHANICAL MEANS FOR ROTABLY OSCILLATING AT LEAST ONE SAID CUP MEMBER ABOUT A POLAR AXIS OF TIS SAID ZONAL REGION, MECHANICAL MEANS FOR ROTATING THE REMAINING SAID CUP MEMBERS; AND MECHANICAL FORCE MEANS CONNECTED TO ONE OF SAID CUP MEMBERS FOR URGING SAID ONE OF SAID CUP MEMBERS AGAINST SAID SPHERICAL SURFACE AND URGING SAID SPHERICAL SURFACE AGAINST THE OTHER OF SAID CUP MEMBERS. 